The present invention relates in general to propulsion systems, and more particularly to a propulsion system for a water vehicle.
Water jet propulsion systems have been disclosed in the following U.S. patents:
U.S. Pat. No. 3,809,005, issued on May 7, 1974, to the applicant of the present application for Propulsion System;
U.S. Pat. No. 3,336,752, issued on Aug. 22, 1967, to M. S. Smith for Jet Boat Propulsion Unit;
U.S. Pat. No. 3,283,737, issued on Nov. 8, 1966, to C. A. Gongwer for Jet Propulsion Device For Water Vehicles;
U.S. Pat. No. 3,212,258, issued on Oct. 19, 1965, to C. A. Gongwer for Water-Jet Propulsion Device For Boats.
Another patent of interest is the U.S. patent to George F. Wislicenus, U.S. Pat. No. 3,575,127, issued on Apr. 13, 1971, for Vehicle Propulsion Systems.
It has been heretofore known that the adjustment of the thrust line angle can provide improved performance in propulsion systems for boats and particularly the performance of boats employing planing type hulls. Outboard engines have been provided with a series of holes and movable pins to provide for the adjustment of the thrust line angle. The inboard/outdrive propulsion systems have employed complex electro-hydraulic systems and electro-mechanical systems to adjust the thrust line angle for improved performance. Additionally, the inboard/outdrive propulsion systems have employed a series of holes and movable pins and hydraulic power trim systems for adjusting the thrust line angle for improved performance. Tilt cylinders have also been employed in the past. In jet propulsion systems, there was either no adjustment, a manual adjustment or a power adjustment. As part of a jet propulsion system, a complex electro-hydraulic and electro-mechanical system were employed for adjusting the thrust angle for improved performance.
It has been known that the efficiency of a jet propulsion system is related to the size of the nozzle. Large nozzles permit a maximum flow rate of water which results in maximized propulsive efficiency. It has also been found that a reduced nozzle size minimizes the tendency to cavitate which can cause a gross loss of performance in the lower speed range, i.e. 8-20 miles per hour. A conventional nozzle is generally arranged to minimize the size of the nozzle and the flow rate of water to prevent cavitation. The failure of a nozzle to maximize the flow rate of water and to minimize the cavitation resulted in greater fuel consumption, greter engine noise and reduced engine life.
In the patent to Rodler, Jr. U.S. Pat. No. 3,809,005, the shield or deflector for reversing the direction of thrust had an annular configuration and a series of arc-shaped forward jet ports which produced essentially an annular jet. The annular jets were not totally effective in clearing foreign matter entrained in the water about the intake duct. The deflector was not fully effective in controlling reverse water flow.